Photochromism is a reversible function that a certain compound changes its color when it is irradiated by sunlight or light including ultraviolet radiation such as light from a mercury lamp and returns to its original color when it is placed in the dark by stopping the irradiation, and used for various applications. Fulgimide compounds, spirooxazine compounds and chromene compounds have been found as photochromic compounds having this photochromism. Since optical goods having photochromic properties can be obtained from complexes of these compounds and plastics, a large number of studies on complexes of photochromic compounds are now under way.
For example, photochromism is applied in the field of eyeglass lenses. A photochromic eyeglass lens comprising a photochromic compound is quickly colored outdoors where it is irradiated by light including ultraviolet radiation like sunlight to serve as a sunglass lens and faded indoors where there is no irradiation to serve as an ordinary transparent eyeglass lens. Demand for this kind of lenses is growing nowadays.
Plastic photochromic eyeglass lenses are particularly preferred from the viewpoints of lightweight and safety. To provide photochromic properties to these plastic lenses, the above photochromic compound is generally compounded. As means of compounding the photochromic compound, there are known a method in which the surface of a lens having no photochromic properties is imbibed with a photochromic compound (to be referred to as “imbibition method” hereinafter) and a method in which a photochromic compound is dissolved in a monomer and the monomer is polymerized to obtain a photochromic lens directly (to be referred to as “casting method” hereinafter). Various proposals are made for the imbibition method (U.S. Pat. Nos. 5,739,243, 5,973,093 and WO95/10790) and the casting method (JP-A 5-306392, WO96/037574, WO01/005854, WO01/092414, WO02/028930 and WO2004/083268).